EP0237575A1 - Mold assembly - Google Patents

Abstract

Mold assembly for molding an article. The mold assembly consists of at least one male mold and one female mold. At least one of the male and female molds consists of a composition having high strength and containing hydraulic material as the main ingredient. A molding face of at least one of the male and female molds consists of a substance other than the hydraulic material.

Description

DESCRIPTION

TITLE OF THE INVENTION: Hold Assembly

BACKGROUND OF THE INVENTION:

Field of the Invention?

5 The present invention relates generally to a mold

assembly for molding an article, and more particularly to such

a mold assembly which is made of a hardened hydraulic material

composition having high strength.

Related Art Statement;

i° " Conventional molds or mold assemblies are made of cast irons, steels, zinc base alloys, aluminum or various

resins. However, molds made of cast irons, steels, zinc.base

alloys or aluminum are. expensive, since many cumbersome

machining steps and long operation times are required for the

15 production thereof. On the other hand, although a mold made

of a resin can be fabricated relatively easily, a mold made of a resin cannot withstand a high temperature environment and

hence cannnot be used for molding a material which requires heating for hardening.

20 There is, therefore, a demand for a mold assembly

- ~ which can be fabricated or shaped by a simple operation within

a short time period and is excellent in durability.

Since cement concretes are moldable at room

temperature and handled readily, they are used for various applications in the arts of civil engineering and building construction. However, any of the conventional cement mortars and concretes could not be used for making a mold or mold assembly, since they have insufficient strength of less than 1000 kgf/cra² in compressive strength and have the intentions of bleeding or other material separation problems, leading to inferior profiling or shape-reproducing property. OBJECTS AND SUMMARY OF THE INVENTION:

Accordingly, a principal object of this invention is to provide a mold assembly which can be fabricated at room temperature by a simple operation within a short fabrication time and which is high in compressive strength and excellent in durability.

Another object of this invention is to provide a mold assembly made of a material which is free of bleeding or other material separation problems and excellent in profiling property.

A further object of this invention is to provide a mold assembly which can be produced at a low cost and can mold a molded article having a complicated contour and yet with a good finished surface.

Another object of this invention is to provide a mold assembly which can press-mold a metallic material only by fabricating a male mold. A still further object of this invention is to

provide a mold assembly for press-molding a metallic material deeply without leaving scratches or other damages on the

processed surface.

Another object of this invention is to provide a mold assembly suited for molding a resin material.

Another object of this invention is to provide a

mold assembly suited for molding a resin through the reaction

injection molding method.

_^ Yet a further object of this invention is to provide

a mold assembly which is easily assembled with a molding

machine so as to be capable of molding an article without

causing breakdown or damage of the molds and without causing

flawed or disfigured molded articles. Another object of this invention is to provide a mold assembly having a molding face covered by a plated layer

firmly attached to the matrix material and deposited by a simple

non-electrolysis plating.

The above and other objects of the invention will

become apparent from the following description.

A mold assembly for molding an article, according to the invention, comprises a male mold and a female mold,

at least one of said male and female molds being made of a

hydraulic material composition having high strength containing a hydraulic material as a main ingredient, a molding face of at least one of said male and female molds being made of a substance other than said hydraulic material. BRIEF DESCRIPTION OF THE DRAWINGS: 5 Figs. 1 (a) to (d) are flow diagrams showing, in section, a process wherein a male mold of the invention is used in combination of a female mold constituted of a fluid.

Fig.2 is a diagrammatical sectional view showing a mold assembly of the invention, wherein a rubber-like elastomer ° 'is used as the female mold.

Fig. 3 is a diagrammatical sectional view showing another mold assembly embodying the invention, wherein a metal mold is used as the female mold.

Fig. 4 is a diagrammatical sectional view showing 5 another mold assembly embodying the invention, the mold assembly being particularly suited for the reaction injection molding method.

Figs. 5 and 6 are diagrammatical sectional views showing mold assemblies provided with attachment means for the convenience of combining the same with molding machines. DESCRIPTION OF THE INVENTION:

The present invention will be described in detail hereinbelow.

The mold assembly of the invention for molding an article includes male and female molds, optionally combined with one or more blank holders, as desired. According to the principal feature of the invention, either one or both of the male and/or female molds are- made of a hydraulic material composition having high strength. Either one or both of the molding faces of male and/or female molds are made.of a substance other than the hydraulic material composition. Either one of the male or female mold may be, of course, made of a substance other than the hydraulic material composition in its entirety. However, if one of the male or female mold is made of a substance other than the hydraulic material composition in its entirety, at least a portion of the other mold should be made of the hydraulic material composition. On the other hand, if both of the male and female molds are made of the hydraulic material composition, at least one of the molding faces of male and female molds should be made of a substance other than the hydraulic material composition. The blank holder may also be made of the hydraulic material composition. With such a construction, a mold assembly adapted for molding or otherwise shaping a variety of articles can be produced by a simple way within a short fabrication time, with the merit that the mold assembly exhbits excellent fidelity in profiling property.

In consideration of the requirement that the

hydraulic material composition containing a hydraulic material

as the main ingredient may preferably have a compressive

strength of not less than 1000 kgf/cm² and preferably have a

capability of profiling and molding a molded article having

complicated shape, a preferred hydraulic material composition

used in the practice of the invention contains, other than the

hydraulic material, an ultra-fine particle, a water reducing

agent and optionally with other necessary additives. It is desirous that the water content of the composition is as small

as possible.

The hydraulic materials which may be used in the

present invention include various kinds of cements, mineral

materials, combinations of materials having hydraulic activities

and activators, and mixtures thereof. Examples of cements are

various Portalnd cements, such as normal Portland cement, high

early strength Portland cement, moderate heat Portland cement,

white Portland cement and sulfate resisting Portland cement;

various oil well cements; blended cements, such as silica-

cement, fly ash cement and blast furnace cement; and mixtures thereof.

Representative examples of the mineral materials

which may be used as the hydraulic material in the composition

of the invention are mineral materials of Ca₃Si0_s, solid solution of Ca₃SiO_s and mixtures thereof. One example of the

solid solution of Ca₃SiO_s is alite which is one of the main constituent minerals of general cements. Although somewhat

different stoichiometric formulae have been proposed by

individual research workers, the generally accepted formula thereof is Ca₁₀sMg_zA10_3E (AlSi_3S0₁₄₄) , as reported by G. Ya aguchi and S. Takagi, Proc. 5th Int' 1 Symp. Chem. Cement, Tokyo, 1, 181—225 (1968), with optional other trace

constituents. A variety of chemical formulae may be considered

depending on the kinds and quantities of components contained in

minerals of.Ca₃SiO_s and solid solutions of Ca₃Si0₅. The

minerals of Ca₃Si0₅ and/or solid solutions of Ca₃SiO_s used in

the invention have the analytical values of X-ray

diffractiometry generally agreed with those of Ca₃SiO_s and alite

recorded in the JCPDS cards.

The materials having hydraulic activities include

blast furnace slag, fly ash and mixtures thereof. Such a

material generally has an average particle size of from 10

to 30 μ m , and has no hydraulic property in itself but it is hardened to form a rigid mass when combined with an activator.

Activators which may be combined with such materials having

hydraulic activities to harden the same have been known in

the art, and include a variety of cements; calcium hydroxide; calcium oxide; quick lime; calcium sulfoaluminate minerals; a variety of inorganic and organic alkalline salts, such as carbonates, bicarbonates, hydroxides, silicofluorides and sodium, lithium and potassium salts of gluconic acid and citric acid; and calcium sulfates, i.e. anhydride, hemihydrate and dihidrate of calcium sulfate. Any one of the aforementioned activators may be used singly or two or more of them may be used in combination. Any one or more of these activators may be added in an amount which varies depending on the required properties ajid the specific kind or combination of the activator used, and it is desireous that not more than 100 parts by weight, preferably not more than 60 parts by weight, of an activator is admixed with 100 parts by weight of the material having hydraulic activity. The particularly preferred material

having hydraulic activity is blast furnace slag.

When a substance which releases Ca(0H)₂ upon contact with water such as calcium hydroxide, calcium oxide, quick lime, or cements is used as an activator, it improves the fluidity of the entire composition significantly in cooperation with the action of the ultra-fine particle and the water reducing agent, with the result that the ultra-fine particles are dispersed uniformly in-between the particles of the hydraulic material under the action of the water reducing agent to Increase the strength of the final solidified mass remarkably. In order to attain the aimed function of improving the fluidity of the

composition by the addition the substance releasing Ca(0H)₂ upon

contact with water, it suffices to add such a very small

quantity that to 100 parts by weight of the total amount of the

hydraulic material and the ultra-fine particle there is added not more than 1 part by weight, preferably not more than 0.5

parts by weight, of the Ca(0H)₂-releasing substance.

The combination of the aforementioned material having

hydraulic activity and the activator is only slightly exothermic

to reduce or prevent thermal cracking due to exothermic heat,

and in addition has further advantages such that the contraction

by hardening or drying of the composition is decreased, and that

• the composition containing such a material having hydraulic

activity is improved in resistance to chemicals.

The composition used in the invention may be added with, in addition to the hydraulic material, an additive,

such as an expansive additive, a rapid hardening agent, a mixing

additive for exhibiting high strength, an accelerator and a

retarder. Preferable expan-sive additives are ettringite type

expansive agents, such as "CSA #20" (Trade Name) available from

Denki Kagaku Kogyo K.K., and burnt quick limes, particularly

burnt quick lime prepared by burning at a temperature of from

1100 to 1300°C and having an -average grain size(diameter) of not

more than 10 microns. On the other hand, examples of preferable 1 0

rapid hardening agents are calcium alu inate system materials, such as alumina cements or combinations of alumina cements with calcium sulfate, the one sold under the Trade Name of "Denka ES" from Denki Kagaku Kogyo K.K., and the one sold under the Trade Name of "Jet Cement" from Onoda Cement Co., Ltd. Examples of effective mixing additives for exhibiting high strength are calcium sulfate system materials, such as the one sold under the Trade Name of "Denka ∑-IOGO" from Denki Kagaku Kogyo K.K. and the one sold under the Trade Name "Asano Super Mix" from Nippon Cement Co., Ltd.

Examples of accelerators are chlorides such as calcium chloride, thiocyanates, nitrites, chromates and nitrates. Examples of retarders are saccharides; soluble dextrin; organic

acids and salts thereof such as gluconic.acid; and inorganic salts such as fluorides.

In ageing the hydraulic material composition used in the invention, it is preferred that the ageing operation includes high temperature ageing effected at about 50°C to 250^βC or includes high temperature and high pressure ageing effected at about 50^βC to 250°C in order to obviate continuation of reaction extending over too long ageing period and thereby to improve the stability of the aged mass. It is also possible to compensate the contraction by the use of an expansive cement, to

allow exhibition of required strength for a relatively short 1 1

ageing time by the use of a rapid hardening cement, or to

increase the strength of the hardened mass by the use of a calcium sulfate system mixing agent for exhibiting high strength.

The ultra-fine particle used in the invention may

preferably have an average particle size which is smaller

by at least one order than the average particle size of the hydraulic material which ranges generally within 10 to 30 μ m .

More specifically, it is desirous that the average particle

size of the ultra-fine particle ranges not more than 3 μ m ,

preferably not⁷ more than 1 μ m., and more preferably from about 0.1 to 1 μm. By the addition of the ultra-fine particle,

exhibition of strength is enhanced and the fluidity of the

composition is increased. Examples of preferable ultra-fine

particles are silica dust or silicious dust obtained as the

by-products in the preparation of silicon, silicon-containing alloy or zirconia, and other materials which may be used in the

invention include calcium carbonate, silica gel, opalic silica, fly ash, blast furnace slag, titanium oxide and aluminium oxide.

Any of the mineral materials of Ca₃Si0_s and solid solutions of

Ca₃Si0_s may be pulverized in a ultra-fine particle form

which may also be used as the ultra-fine particle in the . composition of the invention. Hydrate contraction of the

composition can be effectively suppressed by the use of

ultra-fine particles of opalic silica, fly ash and blast 1 2

furnace slag prepared by pulvering them by the combined use of

a classification separator and a pulverizer.

Two or more different kinds of ultra-fine particles

may be used in combination. For example, 100 parts by weight

of ultra-fine opalic silica, fly ash or blast furnace slag is mixed with not more than 75 parts by weight- of ultra-fine silica fume particle to use as the ultra-fine particle component

in the composition used in the invention.

The ultra-fine particle is used preferably in an

amount so that 6θ to 95 parts by weight of hydraulic material

is mixed with 5 to 40 parts by weight of ultra-fine particle,

and more preferably in an amount_._so that 65 to 90 parts by

weight of hydraulic material is. mixed with 10 to 35 parts by

weight of ultra-fine particle. If the amount of the ultra-fine

particle is less than 5 parts by weight, the strength of the hardened composition may be lowered below the satisfactory level;

whereas if the amount of the ultra-fine particle is more than

40 parts by weight, the fluidity of the kneaded composition may

be lowered to a level to pose difficulty in molding operation

and the strength of the hardened composition may be lowered to

unsatisfactory level.

1 3

The water reducing agent used in the invention is a

surface active agent which has a high dispersibility and which may be added to a hydraulic material in a large quantity

without accompanying excessively early or retarded setting and

without excess air entrainment. Examples of the water reducing agent which may be preferably used in the composition of the

invention include those mainly composed of salts of condensation product of naphthalenesulfonic acid and

formaldehyde, salts of condensation product of alkylnaphthalene-

sulfonic acid and-formaldehyde, salts of condensation product

of melaminesulfonic acid and formaldehyde, high molecular

weight ligninsulfonates and polycarboxylates. In consideration

of the effect in improving the fluidity and economy, it is

preferred to us salts of condensation product of naphthalene-

sulfonic acid and formaldehyde or salts of condensation product

of alkylnaphthalenesulfonic acid and formaldehyde. Preferably

not more than 10 parts by weight, more preferably 1 to 5 parts

by weight, of water reducing agent is added to 100 parts by

weight of hydraulic material. The water reducing agent is

added with the aim to preparing a composition having a low

water/(hydraulic material + ultra-fine particle) ratio, and the addition thereof in excess of 10 parts by weight may

adversely affect the hardening of the composition. In the

present invention, a water reducing agent is combined with 1 4

a ultra-fine particle so as to obtain a hydraulic material

composition which has a fluidity high enough for molding by

ordinary molding operation even when the water/(hydraulic

material + ultra-fine particle) is not more than 25$.

Although some amount of water is necessary for

molding the composition, the water content should be as small

as possible for obtaining a hardened mass having high strength, and it is preferrred that 100 parts by weight of the mixture of hydraulic material with ultra-fine particle is

added with 10 to 30 parts by weight, more preferably 12 to 25

parts by weight, of water. It may become hard to obtain a

hardened mass having high strength if more than 30 parts by

weight -of water is added, whereas difficulties are encountered

in molding the composition through ordinary processes, such as

casting, if the added amount of water is less than 10 parts by

weight. However, the water content is not always limited to

the defined range, for example, a composition added with less

than 10 parts by weight can be molded by the compression

molding process. The composition of the Invention may be

molded through any process generally used for molding ordinary

cement concrete compositions, including the extrusion molding

process.

In general, the composition of the invention is added

with a variety of aggregates. Any of the aggregates generally used for aggregate in the fields of civil engineering and building construction may be used in the composition of the

invention, the usable aggregates being river sand, mountain

sand, seashore sand, crushed sand, slag sand, crushed rock,

river gravel, slag gravel and light-weight aggregates. It is preferred, with a merit of considerable improvement in

strength, to use an aggregate selected to have a Moh' s hardness of not less than 6, more preferably not more than 7, or in

accordance with another standard, to have a Knoop indentor

hardness of not less than 700 kg/mm² , more preferably not less

than 800kg/mm². Examples of the aggregates satisfying the

aforementioned requirements defined by either one of the

standards are silica, emery, pyrite, ferrite, topaz, lawsonite,

diamond, corundum, phenacite, spinel, beryl, chrysoberyl,

tour oline, granite, andalusite, staurolite, zircon, burnt

bauxite, calcinated alum shale, boron carbide, tungsten

carbide, ferrosilicon nitride, silicon nitride, fused silica,

electrofused magnesia, silicon carbide, cubic boron nitride and crushed ceramics. Metallic materials, such as iron

or stainless steel, may also be used when it is desired to

subject the hardened mass to further machining operation.

An aggegate may generally be used in an amount such

that not more than five times in weight of the aggregate is

added to unit weight of the sum of the hydraulic material and the ultra-fine particle, when the composition is molded by normal casting process. The added amount of the aggregate would vary out of the aforementioned range when the composition

of the invention is molded through the- prepacked process

wherein an aggregate has been preliminarily placed in situ

and then the composition in the form of paste or mortar is

cast or poured over the aggregate, or when the composition of the invention is molded by the post-packed process wherein the aggregate and the mortar are placed in the vice versa

sequence.

Various fibers or nettings may be admixed as rein¬

forcing materials. Examples of fibers suited for this purpose

are various natural and synthetic mineral fibers, such as steel

fibers, stainless steel -fibers, asbestos fibers and alumina

fibers, carbon fibers, glass fibers, and natural and synthetic organic fibers, such as propylene, Vinylon, acrylonitrile, polyamide synthetic fibers and cellulose fibers. It is also

possible to use other reinforcing materials which have been

conventionally used for such purpose, the examples being steel

rods or FRP rods.

Materials affording other functions, for example for affording slidability, may be contained in the composition.

For instance, a so-called solid lubricant, such as molybdenum

disulfide, hexagonal boron nitride or carbon which may be 1 7

impregnated with oil, may be added to the composition of the

invention.

A material for affording special functions, such as

thermal conductivity or electrical conductivity, may also be

added. The process and sequence of addition in mixing and

kneading the aforementioned additives are not critical as far

as they can be mixed and kneaded to form a uniform admixture.

Alternatively, vacuum debubbling may be effected during the

kneading and molding operations. Ageing _of the molded mass may be effected by any

methods including ageing at room temperature, ageing with.

vapor at atmospheric pressure, ageing at high temperature and

at high pressure and ageing at high temperature. These methods

may be combined.

The mold assembly of the invention for molding an article will now be described with reference to the appended drawings.

An embodiment of the mold assembly of the invention

is generally denoted by reference numeral 10 in Figs. 1(a) to (d)

and Fig. 2. As shown in Fig. 1(a), the mold assembly 10 includes a male mold 11, a female mold 12 and a blank holder 13.

The female mold 12 shown in Fig. 1(a) is constituted of a fluid,

such as water, oil or air with or without being pressurized,

sealingly contained in a defined volume by means of a resilient 1 8

membrane, such as a rubber membrane 14. The female mold 12' shown in Fig. 2 is constituted of a rubber-like elastic material, such as a urethane rubber in its entirety. In both of the embodiments shown in Figs. 1(a) and 2, the male molds 11 are made of a cement composition having high strength.

Referring now to Figs. 1(a) to (d), a, process for press-molding a metal plate 15 by means of the mold assembly 10 will be described. The molding process using the mold assembly 10 shown in Fig. 2 is similar to the process shown by Figs. 1(a) to (d), and will not be described repeatedly. As shown in Fig. 1(b), as the male mold 11 is pushed into the female 12 while holding the marginal portion of the metal, plate 15 by the blank holder 13,- a fluid pressure is applied on the metal plate 15 so that the metal plate 15 is press-molded. Then, the male mold 11 is pulled off together with the blank holder 13 as shown in Fig. 1(c), and the blank holder is raised as shown in Fig. 1(d) to separate the molded metal plate 15 to complete the process. Since a variety of articles having different contour and dimensions can be formed only by changing the male molds 11 when the embodiments shown in Figs. 1 and 2 are used, these embodiments are suited to the applications where a variety of different lots of products each having different contour and di entions with each lot including a small number of products may be produced. Since the female molds 12 and 12' are made of a fluid or a rubber-like elastic material, the

upper surface of the metal plate 15 is not scratched or damaged

during the pressing step. The surface, i.e. the molding face

of the male mold 11 may be covered by a metal layer, a layer of

a resin, such as an epoxy resin or an epoxy resin composition containing metal particles, or a layer of a ceramic material,

such as alumina, alu ina-titania, magnesia or spinel. Such a

covering layer may be deposited by a plating, flame spraying,

coating or impregnating method.

Another embodiment of the mold assembly of the

invention is denoted by reference numeral 30 in Fig. 3. The

mold assembly 30 comprises a male mold 31, a female mold 32 and

a blank holder 33. The male mold 31 is made of a cement

composition having high strength, and has a mol -frame 31a and

reinforcing steel wires 31b. The female mold 32 is made of a

metallic material, for example, cast iron, steel or stainless

steel, a variety of alloys such as a zinc base alloy or a non-

ferrous metal such as aluminum, and may be shaped to have a

desired contour and dimensions by casting or tracer controlled

milling. The blank holder 33 is made of a cement composition having high strength. Although the female mold 32 is made of a

metallic material in its entirety in the illustrated embodiment,

a molding face 32a made of a metallic material may be provided

as a surface layer. In such a case where only the surface layer is made of a metallic material, the surface layer may be formed

by a plating, flame spraying or electoro-plating process on a

matrix made of a cement composition having high strength or a

resin concrete containing an epoxy resin as the main resinous

ingredient.

By using a mold made of a cement composition having

high strength and a mold made of a metal in combination, a

metal plate such as an iron plate, a steel plate, various alloy plates, such as a stainless steel plate, and non-ferrous metal plates, may be easily molded by press molding. It is

generally preferred that the male mold 31 and the blank holder

33 are made of a cement composition having high strength, and

that the female mold 32 is made of a metallic material, in order

to produce a product having good surface conditions. Although

it is the most economical measure to make both of the male and

female molds from a cement composition having high strength,

such a measure is not recommendable since creases due to squeezing are formed when a metal plate is processed through a

deep drawing by the use of a mold assembly wherein both of the

male and female molds are high in hardness. By the use of a

female mold made of a metallic material, the product has a

better surface condition as compared with that processed by

using a mold assembly wherein both of the male and female molds

are high in hardness. A further embodiment of the mold assembly of the

invention is denoted by reference numeral 40 in Fig. 4. The

mold assembly 40 contains a male mold 41 and a female mold 42,

and both of the male and female molds 41 and 42 are made of a

cement composition having high strength. The male mold 41 and the female mold 42 have, respectively, metal plating layers 41a

and 42a. The male mold 41 and the female mold 42 are fixed to

metal frames 41b and 42b.

The mold assembly 40 of this embodiment is particu-

larly suited for molding an article by the reaction injection

molding (hereinafter referred to as RIM) process comprising the

steps of introducing two main reactants of liquid form, each of

the reactants having a low molecular weight, a low viscosity

and a high reactivity, into a mixing chamber under a high

pressure to allow them to impinge and mix with each other, and

then injecting the mixture in a closed mold cavity to react

within a short time to be solidified. The RIM process has been

developed for molding a urethane resin by a high speed molding

process, and the greatest merit thereof, when compared with the

conventional injection molding process for thermoplastic resins, resides in that starting materails having high activities may be used. Application field of the RIM process

is now spreading so as to be used for molding, not only urethane

resins but also other resins, such as nylon, epoxy resins and polyester resins, and for molding polymer composite materials made of, for example, an urethane resin and an epoxy resin, or an urethane resin and a polyester, resin. As a material for a mold assembly used in such RIM process, iron, aluminum, zinc alloys and nickel have been predominantly used in the prior art. In general, the material for a mold ase bly used in the RIM process is selected in consideration of the durability, resistance to abrasion and cost, and an important factor for the selecsion of the aterail therefor is that it has high thermal conductivity and forms a good skin layer_* Since the RIM process is suited for producing small numbers of various articles each having different shape and dimensions, it provides a particular advantage of reduction of operation time if the process for preparing a mold assembly for use in the RIM process can be simplified. Since the mold assembly 40 of the invention is made of a cement composition, the time required for the preparation of the mold assembly is about a week which is remarkably shorter than the time required for the preparation of the conventional mold assembly costing 12 to 22 weeks. As shown in Fig. 4, a liquid high molecular weight resinous mixture is injected under high pressure into a sealingly closed cavity of the mold assembly 40 and is molded therein. The molded article 43 may be used as it is or may be

coated with a variety of coating compositions ready for use as a part. A releasing agent may be used to prevent the molded article from adhering to the mold faces, when a urethane resin

is molded in the mold assembly. For this purpose, various

releasing agents may be used, the examples being silicone resin

base releasing agents, wax base releasing agents and surfactant base releasing agents.

The surfaces of the molds 40 made of a hardened

cement composition may be covered with metal plating layers 41a and 42a which are then subjected to mirror finishing, when an

article satisfying a high accuracy requirement is molded.

In order to cover the molding faces of the mold made

of a hydraulic material composition with metal plating layers,

a non-electrolysis plating method may be adopted. In detail,

when the surface of the hardened hydraulic material composition

is stained with oily materials, such as a releasing agent, the

surface is rinsed with a rinsing agent, such as acetone, for

dissolving oily materials and water, and then washed with

water, or the oily materials are rinsed with an oleophilic

solvent, such as trichloroethylene, followed by drying.

Thereafter, the mold matrix made of the hardened hydraulic

material composition is dipped in a weakly acidic solution of

a salt of platinum group element, such as a salt of palladium,

which acts as a catalyst, or such a solution is sprayed over

the surface of the mold matrix, to form a skin membrane 24

provided with a catalytic activity over the surface of the mold matrix. Examples of the salts of platinum group elements which may be used for this purpose include salts of Pd, Ru, Rh, Os, Ir and Pt, the representative example being palladium chloride.

The condition for forming such a skin membrane provided with catalytic activity is not critical, and the skin membrane may be formed by allowing the surface of the mold matrix to contact with a solution containing any of the aforementioned salts at room temperature for 1 to 5 minutes. The concentration of the water-soluble salt of platinum group element, such as palladium chloride, is not critical, and generally used is a solution containing 0.001 mol/β to 0.002

mol/β of such a salt. In-order to stabilize the water-soluble salt of platinum group element, such as palladium chloride, an acid, such as hydrochloric acid, may be mixed in an amount of about 1X10~³ mol/β .

Although the mechanism for forming a skin membrane provided with catalytic activity readily on the surface of the mold matrix made of the hydraulic material composition has not been clarified, it is estimated by us that the deposition of catalyst is attributed to the following reaction. When the hydraulic material composition is allowed to contact with a solution of a catalyst, by dipping it in the solution or by spraying the solution onto the surface of the hydraulic

material composition, the platinum group cations in the

solution is reduced by the action of calcium contained in the

hydraulic material composition to thereby be deposited on the

surface of the hydraulic material composition to form a skin membrane having catalystic activity. A catalyst layer

can be readily formed over the surface of the mold matrix

without the need of using an agent for reducing the catalyst. Since a catalyst layer is formed by direct reaction taking place

between the matrix composition and the solution containing the catalyst constituent, the processing time for imprgnating the

mold with the solution is advantageously reduced when compared

with the conventional process. The mold matrix made of the

hydraulic material composition having the thus formed membrane

or layer provided with catalytic activity is then allowed to contact with a plating solution, by dipping the mold in the

plating solution or spraying the plating solution onto the surface of the mold, to form a plating layer through non-

electrolysis plating method. The plating layer may be made of

copper, nickel, cobalt, tin, silver, gold or a platinum group

metal, or an alloy such as a nickel alloy or a cobalt alloy, or

a composite plating composition composed of a metal and a

ceramic material. The conditions for plating vary depending on

a plating bath used and the thickness of the plating layer to be deposited, and are not critical for the practice of the invention. In general, copper plating may be deposited at room temperature, and nickel plating may be deposited at a temperature of from 70 to 100^CC. As will be understood from the foregoing, a skin membrane of a platinum group element, such as palladium, providing catalytic activity is formed to be ready for the subsequent non-electrolysis plating only by dipping the mold in a solution of a salt of palladium group element, such as palladium chloride, without the need of etching by a solution of chromic acid-sulfuric acid and without the need of dipping into an acidic solution of stannous chloride containing stannous chloride and hydrochloric*acid used conventionally as a catalyst reducing agent for palladium chloride. In the prior art process for forming a skin layer of a platinum group element, such as palladium, having catalytic activity, stannous chloride is used as a catalyst reducing agent to reduce a salt of platinum group element, such as a salt of palladium, to deposite the platinum group element, such as palladium.

The surface layer formed by the non-electrolysis plating may be applied with a further coating through an electrolysis plating method, or the hydraulic material composition is rendered to be conductive, and then applied with an electrolysis plating layer. The layer formed by electrolysis

plating method is made of, for example, nickel, chromium, zinc,

gold, silver, tin, various alloys and composite plating

materials combined with ceramics. The surface of such

a plating layer may be ground by water sanding paper to have mirror finish. A preferable water sanding paper is # 200 paper

or the like.

A particularly excellent plating layer may be formed

on a hydraulic material compoisiton having a dense structure.

A dense hydraulic material compoisiton contains, for example,

a hydraulic material, an ultra-fine particle, a water reducing

agent, an aggregate and water; or comprises a hydraulic

material as the main ingredient, a hydrophilic high polymer

(hereinafter referred simply to as "high polymer") and water.

The volume percentage of voids or pores (hereinafter referred

to as "porosity") of the dense hydraulic material compoisiton

is not more than 20% for the composition containing a hydrulic

material, an ultra-fine particle, a water reducing agent, an aggregate and water; and the porosity of the dense hydraulic material is not more than 10$ for the composition containing a

hydraulic material as the main ingredient, a high polymer and water.

Examples of the high polymer used in combination

with the hydraulic material include carboxymethyl cellulose, hydroxyethyl cellulose, hydroxyethylmethyl cellulose, hydroxypropylmethyl cellulose, hydroxybutylmethyl cellulose, polyethyleneoxide, copoly ers of acrylamide and acrylic acid, polyacrylamide, copolymers of styrene and maleic anhydride, and polyvinyl alcohol. The high polymer is used in an amount of not more than 30 vt%, based on the weight of the hydraulic material, prferably in an amount of 3 to 20 wt$.

Such a hydraulic material composition having a small porosity has high strength and high surface hardness with the surface excellent in smoothness, and thus can be plated with a metal plating layer of good condition, namely a smooth metal plating layer is formed even when the plating layer is thin. Moreover, the adhesive strength between the metal plating layer and the dense hydraulic material composition- is high. Further embodiments of the mold assembly of the invention are denoted by 50 and 60 in Figs. 5 and 6. The mold assembly 50 comprises a male mold 51, a female mold 52 and a blank holder 53. All of the members 51, 52 and 53 are made

of a cement composition having high strength and reinforced by reinforcing steel wires 51a, 52a and 53a. The female mold 52 and the blank holder 53 are mounted to frames 52b and 53b, and a surface layer 52c is formed on the molding face of the female mold 52. The mold assembly 60 shown in Fig. 6 has a

substantially similar construction as the mold assembly 50, the members corresponding to those of the mold assembly 50

being denoted by similar numerals changing those of the figure

5 into sixties in figure 6. Accordingly, detailed descriptions

of the similar members will not be repeated. The mold 60 has

no blank holder, and a frame 61b is attached to the male mold 61.

The mold assemblies 50 and 60 are provided with

fitting members 54 and 64 for facilitating easy mounting

thereof to molding machines A and B, each of the fitting

members 54 and 64 being made of a material which can be readily

shaped by milling. In the mold assembly 50, the fitting

members 54 are fixed to the molds by means of plural bent nails

55. In the mold assembly 60, the fitting members 64 are

welded to the molds through deformed steel bars 65. The mold

assemblies 50 and 60 can be mounted to the molding machines A

and B at precise positions.

More in detail, when a mold assembly is mounted to

a molding machine, the mounting face of the mold should be machined precisely to have accurate dimensions. If the mounting face is of inaccurate dimensions and shape, the

pressure from the molding machine is not applied uniformly

over the surface of the mold during the molding operation,

leading to breakdown of the mold assembly or production of

inferior molded articles. In order to machine the surface of a mold assembly made of a hydraulic material composition having

high strength to form a mounting face of high accuracy, the

operation time required for completing^* the milling or other

shaping operations is three or four times as long as the time

required for machining operation of a mold made of cast iron,

steel or a zinc base alloy or made of a resin or calcium

sulfate. However, by the provision of the fitting member as

aforementioned, the shaping or machining operation for forming

the mounting face can be completed within a time that is not

longer than the time required for machining a mold made of a

material' other than the hydraulic material composition. The

important property of the material which may be used as the

material for the fitting member is the free-cutting property. Although the-definition of the free-cutting property has not been established, the hardness of the material becomes the lower, the better free-cutting property has the material. It is

preferred that a material used for such purpose has a Rockwell

hardness (measured by the JIS Z 2245 Test Method) of not more

than 40 by E scale.

^' A first method for the provision of such a fitting member comprises the step of placing a backing layer made of a binder selected from resins, calcium sulfates, cements and

mixtures thereof, or a combination of the binder with a filler

having a free-cutting property and selected from air, wood debris, pulp, calcium carbonate particle, metal beads and metal

powders on the hydraulic material composition. A second method is to dispose a machinable metal plate such as a iron plate,

and a third method is to form a backing layer by flame spraying

or plating.

When a cement base material is used as the binder in the first method, the fitting member for engaging with a

molding machine is preferably placed at a time point after the

main body of the mold has been cast and before water has not

yet been evaporated through the face over which the material for the fitting member is placed. The main body and the

fitting member are then aged as an integral mass. When a binder other than the cement base material is used, it is

preferred that the material for forming the fitting member is

cast over the main body of the mold after the main body has been

aged through ageing at room temperature and at atomospheric

pressure, ageing at high temperature, ageing at high

temperature and at a high pressure or a combination thereof.

Nails, anchors or the like members may be embedded in the face

on which the fitting member for engaging with a molding machine

is to be placed at the time when the main body of the mold has

not yet been hardened, thereby to improve the binding between

the main body and the fitting member.

In a case where a plate is placed on the main body of the mold to form a fitting member for engaging with a molding

machine, according to the second method, it is preferred that a

plate material is placed on the upper surface of the main body

before water has been evaporated from the top face of the main

body. In order to increase the binding force between the main body of the mold and the plate material, stud bolts or deformed steel bars may be fixed, for example by welding, onto the

surface of the main body on which the plate material is mounted.

When a fitting member is formed by flame spraying

or plating method, according to the third method, such a layer

is formed after the main body of the mold has been hardened.

A layer may be formed by flame spraying method wherein the

surface of the hardened main body is roughened by sand blasting

to have a surface roughness of about 40 microns, and then a

molten metal or resin is injected onto .the roughened surface.

Since the surface of the hardened main body made of a cement

base composition does not afford metal bond, a plated layer may

be formed through a non-electrolysis plating method. or through

a non-electrolysis plating step followed by an electrolysis plating step.

It is preferable that the thickness of the fitting member for engaging with a molding machine is thin, generally

not more than about 5 cm, since the member is to be cut by

machining and acts as a pressure transferring member during the molding step.

The mold assembly of the invention may be used as a

mold for molding an article made of an admixture of fibers and

a synthetic resin, i.e. a fiber reinforced plastic material

(hereinafter referred to as FRP) . The known molding methods

for molding a FRP using a machine include the sheet molding compound (SMC) and the bulk molding compound (BMC) methods wherein a mixture of fibers and a synthetic resin is molded through press-molding or injection molding and then set or

cured by heating, transfer molding method, the injection molding method and similar molding methods. Amongst them, the

SMC and BMC methods are advantageous since an article having excellent surface condition or property may be prepared within .

a short molding cycle, and thus have been utilized for the

molding of automobile parts, buthtub, building materials and

electrical parts. These methods are expected to be carried

cut by automation systems, particularly with the progress of

substitution of metal parts by plastics in the body of

automobile. The mold assembly of the invention may be effectively used in these molding methods.

Thermo-setting resins, such as unsaturated polyester

resins and epoxy resins, are used generally as the synthetic

resin in the FRP in combination with various fibers, the

typical fibers being fiber glass processed to be hydrophobic. The admixture containing fibers and a synthetic resin as the

main ingredients, means a pre-mix of fibers and a synthetic resin before being subjected to a molding process, and includes,

an uncured mixture and a mixture pre-formed to have a sheet

shape.

The mold assembly of the invention may also be used

for molding an FRP containing an unsaturated polyester resin or an epoxy resin as the resinous ingredient, such a resin being

generally theremo-setting. In such a case, it is necessary to

heat the. FRP to be cured, and heating is effected by disposing

heat adjusting pipes or electrical heating wires within the

mold assembly or by means of external heating. Although the

mold assembly of the invention has a relatively low thermal

conductivity as compared with a mold made of cast iorn or

similar material because the mold assembly of the invention is

made of a hydraulic material, this feature provides a "merit

rather than disadvantage since the once heated mold assembly

is resisting to cooling. The mold assembly of the invention

may also be well suited for use in the injection molding process, the blow-molding -process and the vacuum molding - process.

EXAMPLES OF- THE INVENTION:

The present invention will now be described more

specifically by referring to examples thereof. Example 1

A mold assembly 10 having the construction as shown in Fig. 1 was prepared and, used in this Example.

A male mold 11 for molding an article by press-

molding and a blank holder 13 were produced using the composi¬

tion as set forth in Table 1 through an ordinary method. Steel

bars are incorporated to form a composite structure. The

composition was aged at 20°C for one day, and at 50°C in air

saturated with water vapor for 7 days, A test specimen having

the dimensions of 4X4 16 cm was prepared under the same

preparation conditions, and subjected to test to measure the

compressive strength (according to JIS R 5201 Method). The

results are shown in Table 1. The female mold 12 was

constituted of an oil sealingly enclosed by a rubber membrane 14.

Table 1

(parts by weight)

Cement Ultra-fine Water Redu- Aggregate Fiber Water Compressive Particle cing Agent Strength

80 20 2 120 7 19 1,840 kgf/cm²

Materials Used:

Cement: White Portland cement produced and sold by

Chichibu Cement Co. Ltd.

Ultra-fine Particle: Silica fume (produced and sold by Japan Metals & Chemicals Co., Ltd.) having an average

particle size of 0.1 μ m. Aggregate: Dead burnt alum shale having a particle size

of 0.3 to 1.2 mm. (A product from China)

Water Reducing Agent: A condensation product of β -naphtha- lenesulfonic acid and formalin, produced and sold by

Dai-ichi Kogyo Seiyaku Co. Ltd. under the Trade Name of "Selflow HOP".

Water: City Water

Fiber: Steel fibers cut _^by the chatter cutting (produced

and sold by the Kobe Cast Iron Works Ltd) , and having

a fiber length of 2 mm.

A metal plate 15 was placed on the thus prepared male

mold 11 and the blank holder 13, as shown in Fig. 1(a), and

then the male mold 11 was raised as shown in Fig. 1(b) to

carry out a press-molding. The result was that a steel plate

having a thickness of 0.8 mm could be molded without any problem.

Example 2

A part for a motorcycle was molded using a mold assembly having a construction as denoted by 30 in Fig. 3.

A male mold 31 for molding an article by press-molding and a

^" blank holder 33 were produced using the composition as set forth in Table 1. The ageing conditions were the same as in

Example 1. A female mold 32 was fabricated from cast iron

through an ordinary method.

The aforementioned mold assembly 30 was mounted on a

"600pp-123 Press" available from Kawasaki Yucoh Company Limited, and a 0.8 mm thick steel plate was pressed at a P-pressure of

300 tons and at a C-pressure of 60 tons. The press molding

was completed successfully. Twenty weeks were cost for the

production of a conventional mold assembly having a male mold

and a female mold, both being made of a cast iron, whereas the

mold assembly of the invention wherein only the female mold 31

was made of cast iron could be produced within about one week

with a satisfactory result that a steel plate was press-molded

without imparing the appearance of the molded product.

Example 3

A mold assembly for use in the RIM method was

prepared, the mold assembly having the construction similar

to that denoted by 40 in Fig. 4. Metal plating layers 41a and

42a were formed by a non-electrolysis plating method to deposit _a nickel plating. Both of the main bodies of the male and female molds 41 and 42 were made of the composition as set forth in Table 1.

A polyurethane was used as a resinous material to

mold bumpers for an automobile to obtain parts of good quality. Likewise, a polypropylene and an ABS resin were molded through

the injection molding method while using the similar mold assemblies to mold a horn and a shift lever cover for an

automobile, whereby parts of good quality were produced.

Example 4

A mold assembly made of a cement base composition

and having a construction same as the mold assembly denoted by

50 in Fig. 5 was prepared. The mold was prepared for molding an oil tank for an autocycle, and had the dimensions of

1200X600X400 mm. To be ready for mounting the mold assembly

on a molding machine, the fitting member 54 was machined until the top face of the fitting member had a dimensional accuracy ranging within 3/100 mm relative to the face of the press. A

variety of material set forth in Table 2 was used to form the

fitting member 54 which was cut by about 5 ram. Machining was

effected by using a milling machine Model "FNC-106" available from Makino Milling Machine Company, Limited.

Table 2

Fitting Member for Engaging with Molding Machine Time Cost

(Thickness: about 25 mm) for Milling

None; A bare mold assembly made of a cement base composition 9 hrs. was subjected to milling operation.

A fitting member made of a cement-silica system material was used. (Available from Denki Kagaku Kogyo K.K. under the Trade 6 hrs.

Name of "Denka SL".)

A fitting member made of a resin-wood system material was used. (Available from Kokusai Chemical Company, Limited under the 2 hrs.

Trade Name of "Epoxy Blend Resin Plus Cements WR".) A fitting member made of an epoxy resin base material was used.

(Available from Ciba-Geigy Limited under the Trade Name of 2.5 hrs.

"Λraldite-CW 210".)

A fitting member made of a calcium sulfate-resin system material was used. (A press material available from Fuji Gypsum Company, 3 hrs. Limited.)

In this Example, a cement base composition having high strength was used for casting each of the main body of the mold assemblies , the cement base composition being composed of 80 parts by weight of white Portland cement (available from Chichibu Cement Co . , Ltd . ) , 20 parts by weight of a silica flour (available from Japan Metals & Chemicals Co. , Ltd. ) ,

2 parts by weight of a water reducing agent (available from Dai-ichi Kogyo Seiyaku Co. , Ltd . under the Trade Name of

"Self low HOP") , 150 parts by weight of dead burnt alum shale

(produced in China) having a particle size of from 0.3 to 1. 2 ram and 19 parts by weight of water. The cement base composition was kneaded in a vacuum type Omni-mixer and cast by a vacuum- casting method. The cast products were allowed to stand at 20°C for one day, and then aged at 50°C by steam for one day to

produce the molds.

Each of the mold assemblies 50 made of the cement base composition and fitted with respective fitting members was mounted on a "600pp-123 Press" available from Kawasaki Yucoh Company Limited, and 0.8 mm thick steel plates were successively pressed at a P-pressure of 350 tons and at a C-pressure of 80 tons. Each of the mold assemblies had not been deformed or otherwise damaged to be capable of continuing a further molding, even after 50 shots operations.

Example 5 A mold assembly made of a cement base composition and having a construction same as the mold assembly denoted by

60 in Fig. 6 was prepared for molding a battery cover casing. The mold assembly had the dimensions of 1000X600X400 mm. An iron plate (Initail Thickness Just after Installation: 25 mm) similar to that denoted by 64 in Fig. 6 was assembled in each of the male and female molds 61 and 62 which were made of the same cement base composition and aged under the same ageing conditions as in Example 4. The iron plate 64 was milled by about 5 mm to attain a dimemsional accuracy of 3/100 mm relative to the press face of a molding machine. For the

comparison purpose, the face of a comparative mold vas milled by about 5 mm. The times required for milling operation for

respective samples are shown in Table 3.

Table 3

Fitting Member for Engaging with Molding Machine Time Cost (Thickness: about 25 mm) for Milling

None; A bare mold assembly made of a cement base composition 7 hrs. ^• was subjected to milling operation.

A fitting member made of an iron plate was used. 1.5 hrs.

Using the mold asembly 60 of the invention, 2 mm thick steel plates were successively pressed at a pressure of

150 tons to reveal that it had not been deformed to retain the

capability of molding after 100 shots operations. Example 6

Hardened masses obtained from the compositions as set

forth in Table 4 were rinsed with acetone to clean the surfaces

thereof, dried and then plated with nickel plated layers

through various non-electrolysis plating methods as listed in

Table 4. The results are shown in Table 4.

The plated layers were firmly adhering to the

matrices of all the tested molds immediately after the non-

electrolysis plating process. However, after being subjected to thermal treatment, only the plated layer covering the hydraulic

material composition adhered firmly on the matrix. The plated layers deposited on the resin base matrices were easily peeled

only by the nail scratching test. The nickel plated layer

formed in the practice of the invention had an extremely smooth

surface and excellent adhesive strength.

Table

Note 1: Cement Base Composition Normal Portland Cement 100 parts

(Available from Denki Kagaku Kogyo K.K.)

Water 40 parts

Toyoura Standard Siliceous Sand 200 parts

Calcium Sulfate Base Composition He ihydrate of Calcium Sulfate 100 parts

(Reagent grade) Water 20 parts

Note 2: Ageing Condition for Hardened Matrix Ageing at 20°C for 7 days in dry air. Note 3: Condition for Etching The cement base composition and the calcium sulfate base composition were not etched. The ABS and phenol resins were immersed in a 10$ (by volume) hydrochloric acid solution for 30 seconds.

Note 4; Solution A lOg of stannous chloride and 40 m β of hydrochloric acid were dissolved in water to obtain lfl of Solution A.

Solution B 0.25g of palladium chloride and 2.5 mfi of hydrochloric acid were dissolved in water to obtain 1 β of Solution A.

Note 5: Condition for Plating Using a solution containing 30 g/ β of nickel chloride, 10 g/ β of sodium hypophosphate and 50 g/ of sodium hydroxyacetate, and plating was effected at 70°C for 3, hours.

Example 7 .

The compositions set forth in Table 5 were kneaded in a mixer, and a test specimen having the dimensions of 2 X5 cm was molded under reduced pressure develped by suction from each of the compositions. After the lapse of one day, each test specimen was aged at 20°C in pure water for 7 days. After the completion of ageing, the test specimen was dried at 105°C to obtain a hardened speciemen which was weighed in air and the weight (A) thereof was recorded as the constant weight. Thereafter, each test specimen was immersed in boiled water to fill all pores thereof with water, and the weight of the speci¬ men impregnated with water was weighed in water to learn the weight in water (B) and then weighed in air to learn the weight

in air (C). The porosity of each specimen was calculated from the following equation:

Porosity ($) = [{(C) - (A)}/(B)] X 100 The results are shown in Table 5.

Table 5

Material Used

Cement: Normal Partland cement (Denki Kagaku Kogyo K

Ultra-fine Particle: Silica fume (Elkem Co., Ltd.)

Water reducing agent: Selflow R 155 (Dai-ichi Kogyo

Seiyaku Co., Ltd,) Example 8

Each of the compositions of Run Nos. 5 and 14 was

added with siliceous sand in a ratio such that the weight of

the added siliceous sand was equal to the total weight of

the cement and the ultra-fine particle contained in each composition. A hardened matrix was produced from each admixture similar to Example 7, and the hardened matrix

was plated by non-electrolysis plating using each of the

pre-treating solutions as set forth in Table 6. The results

are shown in Table 6. The plated metal was nickel, and the used non-electrolysis plating solution was prepared by diluting a solution commercially sold under the Trade Name of "Kanigen Blue Shumer" in the standard dilution ratio (catalogue ratio).

The non-electrolysis plating was conducted at 70°C for 3 hours.

Prior to the plating step, each matrix or test piece was rinsed

with trichloroethylene for defatting, followed by drying the

surfaces, and then immersed in respective pre-treating solutions

for 5 minutes. Of course, after removing from each pre-treating solution bath, the matrix or test piece.was rinsed with water

prior to be immersed in the next pre-treating solution.

Table 6

Run Composition Pre-treating Condition of

No. of Matrix Solution Plated Layer

19 Run No. 14 -r Siliceous Sand Solution B Fine

20 Run No. 14 + Siliceous Sand Solution C Fine

21 Run No. 14 + Siliceous Sand Solutions (A+B) Not deposited

22 Run No. 14 + Siliceous Sand Solutions (D+E) Not deposited

23 Run No. 5 + Siliceous Sand Solution B Inferior

24 Run No. 5 + Siliceous Sand Solution C Inferior

25 Run No. 5 + Siliceous Sand Solutions (A+B) Not deposited

26 Run No. 5 + Siliceous Sand Solutions (D+E) Not deposited

The solutions used for pre-treatment are as follows.

Solution A: lOg of stannous chloride and 40 m β of hydrochloric

acid are diluted with water to have a volume of 1 β .

Solution B: 0.25g of palladium chloride and 2.5 m of hydro¬

chloric acid are diluted with water to have a volume of lβ . . ^'

Solution C: The standard solution of a commercially available palladium chloride base pre-treating solution

produced by Japan Kanigen Co., Ltd. and sold under the Trade Name of "Red Shumer".

Solution D: The standard solution of a commercially available

colloidal pre-treating solution containing stannous chloride and palladium chloride, produced and sold by

Hitachi Chemical Co., Ltd. under the Trade Name

of "HS-10113". Solution E: The standard solution of a commercially available

rinsing solution produced and sold by Hitachi Chemical

Co., Ltd. under the Trade Name of "ADP-20113".

The test results showed that the hardened and plated

matrices were In satisfactory condition and plated with nickel

layer which was not peeled by the nail-rubbing test.

Example 9

100 parts by weight of an alumina cement produced and sold by Denki Kagaku Kogyo K.K. under the Trade Name of "Denka

Alumina Cement No. 1" was mixed with 8 parts by weight of a

powder of polyvinyl alcohol produced and sold by Denki Kagaku

Kogyo under the Trade Name of "Denka Poval B-245", and added

with 11 parts by weight of water, followed by mixing by twin

rollers for 5 minutes.

A 2 mm thick sheet made of the aforementioned mixture was discharged from the rollers, and pressed at 120°C and at

50 kg/cm² for 10 minutes, followed by ageing at 50TΣ for 7 days, to obtain a matrix on which a plated layer was deposited

by non-electrolysis plating. The thus obtained matrix had a

porosity of 0.8$. Test pieces of the matrix were deposited

with plated layers similarly as in Example 8 except that the pre-treating solutions set forth in Table 7 were used. The

results are shown in Table 7.

Table 7

Run No. Pre-treating Solution- Condition of Plated Layer

27 Solution B fine

28 Solution C fine

29 Solutions (A + B) Not deposited

30 Solutions (D + E) Not deposited

The test results showed that the hardened and plated matrices were sufficiently dense and plated with nickel layers

which were not peeled by the nail-rubbing test. Example 10

The composition of Run No. 14 in Example 7 was mixed with a siliceous sand to prepare a hardened matrix.

Test pieces made of the hardened matrix were treated with

pre-treating solutions set forth in Table 8 and then immersed

in a non-electrolysis plating bath to be plated with copper. The non-electrolysis plating solution used for plating copper

was consisting of 29 g/ β of copper sulfate, 25 g/ β of sodium

carbonate, 140 g/ β of sodium potassium tartarate, 40 g/ β of

sodium hydroxide and 150 ra β of 37$ formalin. The non-

electrolysis plating was effected at 20°C for an hour. The results are shown in Table 8.

Table 8

Run No. Pre-treating Solution Condition of Plated Layer

31 Solution B Fine

32 Solution C Fine

33 Solutions (A + B) Not deposited

34 Solutions (D + E) Not deposited

Test results showed satisfactory results. It was

also ascertained that the copper plated layers deposited on the surfaces of the hardened matrix pieces had adhesive

strength high enough for resisting to nail-scratching test.

Example 11

A mold assembly made of a cement base composition

having high strength was fabricated using the following

compostion. The fabrication time required for the mold assembly

of this Example was only one week which was remarkably reduced

when compared in terms of the time, generally ranging about 12 to 22 weeks, required for the fabrication of the conventional

mold assembly. Nickel was plated over the molding face of the female mold through a non-electrolysis plating method.

The compressive strength of the hardened cement base

composition was 1,750 kgf/cm². 51

Composition (part by weight) :

Cement: Normal Portland Cement 80

(available from Sumitomo Cement Co. Ltd.)

Ultra-fine Particle: Silica Fume 20

(available from Japan Metals & Chemicals Co.,Ltd.)

Aggregate: Dead Burnt Alum Shale 120

(Particle Size: 0.3 to 1.2 mm)

Water Reducing Agent: "Selflow HOP" 2

(A condensation product of β -naphthalenesulfonic

acid and formalin, available from Dai-ichi Kogyo

Seiyaku Co., Ltd.)

Fiber: Steel Fiber Cut by Chatter Cutting 7

(Fiber Lengh: β = 2.mm, available from Kobe Cast

Iron Works Ltd.)

Water: City Water 20

^■' The aforementioned mold assembly made of the hardened

cement base composition having high strength was used for the practice of the SMC process. The material for SMC comprised

a fiber glass, an unsaturated polyester resin, a hardener, a viscosity increasing agent, a filler and a pigment. The mold assembly was heated by hot air to 150°C, and the material for

SMC was pressed under a pressure of 120 kg/cm². An FRP molded

article having good surface luster was produced. Example 12

A mold assembly made of a cement base composition having high strength was fabricated using the following composition. The compressive strength of the hardened cement

base composition was 1,540 kgf/cm². Nickel was plated over the molding face of the female mold through a non-electrolysis

plating method. Composition (part by weight) :

Cement: Normal Portland Cement 80

(Available from Sumitomo Cement Co. Ltd.)

Ultra-fine Particle: Silica Fume 20

(Available from Japan Metals & Chemicals Co.,Ltd.)

Aggregate: Iron Powder 200

(Available from 0ZEKI.)

Water Reducing Agent: "Selflow HOP" 2

(A condensation product of β -naphthalenesulfonic

acid and formalin, available from Dai-ichi Kogyo

Seiyaku Co. , Ltd.)

Fiber: Steel Fiber Cut by Chatter Cutting 7

(Fiber Lengh: β = 2 mm, available from Aishin

Seiki Co. , Ltd.)

Water: City Water 23

The aforementioned mold assembly made of the hardened

cement base composition having high strength was used for molding a BMC by injection molding. The material for BMC

comprised a glass fiber, an epoxy resin and a filler. The

molding temperature was 150^βC and the injection pressure was

250 kg/cm² , An FRP molded article could be molded under the

aforementioned operational conditions.

Claims

54WHAT IS CLAIMED IS:

1. A mold assembly for molding an article, comprising

a male mold and a female mold, at least one of said male and

female molds being made of a hydraulic material composition

having high strength containing a hydraulic material as a main

ingredient, a molding face of at least one of said male and

female molds being made of a substance other than said hydraulic

material.

2. The mold assembly according to claim 1, wherein said

hydraulic material composition comprises a hydraulic material,

an ultra-fine particle, a water reducing agent and water.

3. The mold assembly according to claim 2, wherein said

hydraulic material is selected from the group consisting of

cements, mineral materials, combinations of materials having hydraulic activities and activators and mixtures thereof.

4. The mold assembly according to claim 3, wherein

said cement is selected from the group consisting of Portland cements, oil well cements, blended cements and mixtures thereof.

5. The mold assembly according to claim 3, wherein said

mineral material is selected from the group consisting of

mineral materials of Ca₃SiO_s, solid solutions of Ca₃SiO_s and mixtures thereof.

6. The mold assembly according to claim 3, wherein said

material having hydraulic activity is selected from the group consisting of blast furnace slag, fly ash and mixtures thereof, and said activator is selected from the group consisting of cements, calcium hydroxide, calcium oxide, quick lime, calcium

sulfoaluminate minerals, inorganic and organic alkaline salts,

calcium sulfate and mixtures thereof.

7. The mold assembly according to claim 6, wherein said activator is selected from the group consisting of calcium

hydroxide, calcium oxide, quick lime, cements, and mixtures

thereof.

8. The mold assembly according to claim 2, wherein said

hydraulic material further contains an additive selected from

the group consisting of expansive additives, rapid hardening

agents, mixing additives for exhibiting high strength,

accelerators, retarders, and mixtures thereof.

9. The mold assembly according to claim 2, wherein said

ultra-fine particle is selected from the group consisting of

silica dust, silicious dust, calcium carbonate, silica gel,

opalic silica, fly ash, blast furnace slag, titanium oxide, aluminum oxide, mineral materials of Ca₃SiO_s, solid solutions • of Ca₃SiO_s and mixtures thereof.

10. The mold assembly according to claim 2, wherein said ultra-fine particle has an average particle size of not more than 3 μ m.

11. The mold assembly according to claim 2, wherein said water reducing agent is selected from the group consisting of

those containing, as the main ingredients, salts of condensation

product of naphthalenesulfonic acid and formaldehyde, salts of

condensation product of alkylnaphthalenesulfonic acid and

formaldehyde, salts of condensation product of melaminesulfonic

acid and formaldehyde, high molecular weight ligninsulfonate,

polycarboxylates, and mixtures thereof.

12. The mold assembly according to claim 2, wherein said hydraulic material composition further includes an aggegate.

13. The mold assembly according to claim 12, wherein said

aggregate has a Moh' s hardness of not less than 6.

14. The mold assembly according to claim 12, wherein

said aggregate has a Knoop indentor hardness of not less than

700 kg/mm².

15. The mold assembly according to claim 12, wherein said

aggregate is a metallic material.

16. The mold assembly aaccording to claim 1, wherein

said substance other than said hydraulic material is selected from the group consisting of fluids, rubber-like elastic materials, metallic materials, resins and ceramicas.

17. The mold assembly according to claim 1, wherein said male mold is made of the hydraulic material composition having

high strength, and wherein said female mold is made of the

substance other than the hydraulic material and selected from the group consisting of fluids and rubber-like elastic materials.

18. The mold assembly according to claim 17, wherein said fluid is one or more selected from the group consisting

of water, oils and air.

19. The mold assembly according to claim 17, wherein said

rubber-like elastic material is an urethane rubber.

20. The mold assembly according to claim 1, wherein said male mold is made of the hydraulic material composition having

high strength, and wherein said female mold is made of a metallic material.

21. The mold assembly according to claim 1, wherein said male and female molds are made of the hydraulic material

composition having high strength, and wherein said molding faces

are made of a metallic material.

22. The mold assembly according to claim 1, wherein a

fitting member made of a material adapted to be easily machined

is provided with said mold assembly at a position for engaging with a molding machine.

23. The mold assembly according to claim 1, wherein said

molding face is a plated molding face.

24. The mold assembly according to claim 23, wherein

said plated molding face is prepared by allowing said hydraulic

material composition containing calcium to contact with a

catalyst solution to deposite said catalyst to form a coating 58

under the action of said calcium and then forming a plated memebrane by a non-electrolysis plating method.

25. The mold assembly according to claim 24, wherein said catalyst solution is a weakly acidic solution of a compound of

platinum group metal.

26. The mold assembly according to claim 24, wherein

said plated molding face is provided over a surface of said

hydraulic material composition having high strength and having

a porosity of not more than 30$.

27. The mold assembly according to claim 1, wherein said

article is made of a material selected from the group consisting of metal plates, resins formed by a reaction

injection molding process, resins formed by an injection molding

process, resins formed by a blow molding process, resins formed

by a vacuum molding process, and mixtures of fibers and synthetic resins.